feat: add Either type

Author: paolobarbolini

benzina/Cargo.toml

@@ -24,7 +24,7 @@ features = [
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-diesel = { version = "2.3", default-features = false, optional = true }
+diesel = { version = "2.3", default-features = false }
 serde_core = { version = "1.0.221", optional = true }
 serde_json = { version = "1.0.144", optional = true }
 schemars = { version = "1", default-features = false, optional = true }
@@ -41,10 +41,10 @@ uuid = { version = ">=0.7.0, <2.0.0", default-features = false, features = ["v4"
 
 [features]
 default = ["derive"]
-derive = ["dep:benzina-derive", "dep:diesel", "dep:indexmap"]
+derive = ["dep:benzina-derive", "dep:indexmap"]
 rustc-hash = ["dep:rustc-hash"]
 
-postgres = ["benzina-derive?/postgres", "dep:diesel", "diesel/postgres_backend"]
+postgres = ["benzina-derive?/postgres", "diesel/postgres_backend"]
 typed-uuid = ["postgres", "diesel/uuid", "dep:uuid"]
 mysql = ["benzina-derive?/mysql"]
 

benzina/src/either.rs

@@ -0,0 +1,62 @@
+use diesel::backend::Backend;
+use diesel::expression::ValidGrouping;
+use diesel::query_builder::{AstPass, QueryFragment, QueryId};
+use diesel::{AppearsOnTable, Expression, QueryResult, SelectableExpression};
+
+/// Either type for Diesel expressions - allows different expression types in match arms.
+#[derive(Debug, Clone, Copy)]
+pub enum Either<L, R> {
+    Left(L),
+    Right(R),
+}
+
+impl<L, R> Expression for Either<L, R>
+where
+    L: Expression,
+    R: Expression<SqlType = L::SqlType>,
+{
+    type SqlType = L::SqlType;
+}
+
+impl<L, R, QS> AppearsOnTable<QS> for Either<L, R>
+where
+    Self: Expression,
+    L: AppearsOnTable<QS>,
+    R: AppearsOnTable<QS>,
+{
+}
+
+impl<L, R, GB> ValidGrouping<GB> for Either<L, R>
+where
+    L: ValidGrouping<GB>,
+    R: ValidGrouping<GB, IsAggregate = L::IsAggregate>,
+{
+    type IsAggregate = L::IsAggregate;
+}
+
+impl<L, R, QS> SelectableExpression<QS> for Either<L, R>
+where
+    Self: AppearsOnTable<QS>,
+    L: SelectableExpression<QS>,
+    R: SelectableExpression<QS>,
+{
+}
+
+impl<L, R, DB> QueryFragment<DB> for Either<L, R>
+where
+    DB: Backend,
+    L: QueryFragment<DB>,
+    R: QueryFragment<DB>,
+{
+    fn walk_ast<'b>(&'b self, pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
+        match self {
+            Either::Left(l) => l.walk_ast(pass),
+            Either::Right(r) => r.walk_ast(pass),
+        }
+    }
+}
+
+impl<L, R> QueryId for Either<L, R> {
+    type QueryId = ();
+    const HAS_STATIC_QUERY_ID: bool = false;
+}

benzina/src/lib.rs

@@ -7,6 +7,7 @@ pub use benzina_derive::{Enum, join};
 pub use self::array::{Array, ArrayWithNullableItems};
 #[cfg(feature = "ctid")]
 pub use self::ctid::{Ctid, ctid};
+pub use self::either::Either;
 #[cfg(feature = "postgres")]
 pub use self::int::{U15, U31, U63};
 #[cfg(feature = "json")]
@@ -22,6 +23,7 @@ pub mod __private;
 mod array;
 #[cfg(feature = "ctid")]
 mod ctid;
+mod either;
 #[cfg(feature = "postgres")]
 pub mod error;
 #[cfg(feature = "example-generated")]